The present invention relates to an inspection method and apparatus for an EL (ElectroLuminescence) array substrate, and more specifically, relates to an inspection method and apparatus for an EL array substrate comprising a drive transistor having the drain connected to one of electrodes of an EL element, a holding capacitor connected to the gate of the drive transistor, a parasitic capacitor formed between the one electrode of the EL element and the gate of the drive transistor, and a switching transistor having the drain connected to the gate of the drive transistor.
FIG. 20 is a circuit diagram showing a configuration of one pixel of an organic EL panel. This organic EL panel is of the so-called voltage writing type, and comprises an organic EL element 1, a drive transistor 2, a holding capacitor 3, a switching transistor 4, a gate line 5 and a data line 6.
When the switching transistor 4 turns on, charge is introduced from the data line 6 so that the holding capacitor 3 is charged. When the switching transistor 4 turns off, writing of a voltage into the holding capacitor 3 is finished and the holding capacitor 3 holds the written voltage. The gate potential of the drive transistor 2 upon the termination of the voltage writing is determined based on the amount of charge charged in the holding capacitor 3. Current that flows through the organic EL element 1 is controlled depending on this gate potential, thereby to control the luminance of the organic EL element 1.
During the fabrication process of such an organic EL panel, ON/OFF failures of the drive transistor 2 and the switching transistor 4 and open/short-circuit failures of the holding capacitor 3 are inspected. This inspection, however, is carried out in the lighting inspection process of the organic EL element 1 after the organic EL panel has been assembled. Accordingly, even if a failure is generated on an organic EL array substrate before the organic EL element 1 is formed thereon, i.e. before the organic EL panel has been assembled, that failure is only detected after the organic EL panel has been assembled. Among failures to be detected, there are those failures that can be put in order on the substrate before assembling, but can not be mended on the panel after assembling. As a result, there arises a problem that the assembling cost becomes vain.